The most important function of absorbent articles such as, for example, diapers, incontinence devices or sanitary towels, is to provide absorption capacity and to afford good leakage protection when bodily fluids such as urine, menstrual fluid etc. are discharged.
Another important characteristic of the absorbent article is that it is pleasant and comfortable to use.
Examples of improvements which have been made with regard to wearer comfort are: increased dryness against the body of the wearer in spite of containing large quantities of liquid, thinner and more flexible articles, and a softer surface against the body of the wearer. Articles which are designed so that unpleasant odour is reduced during use are further examples of improvements made with regard to wearer comfort. Other improvements could be enumerated.
Absorbent articles have also been improved by having been made breathable, that is the absorbent articles have been designed so that they do not function like warm and wet compresses as soon as they have become wet after the first urination or discharge of bodily fluid into the articles. A warm and wet compress is formed if a moist and impermeable absorbent article lies in contact with the skin of the wearer without the possibility of ventilation, that is without the possibility of transporting moisture away from the skin of the wearer. Articles which create warm and wet compresses during use frequently cause the wearer skin irritation problems, especially in the case of long-term use. Those articles which make it possible for moisture to be transported away are referred to within the technical field as breathable absorbent articles. Breathable absorbent articles represent a considerable improvement of the articles with regard to wearer comfort and have also brought about a marked improvement in the skin condition of the wearer during use of the absorbent articles.
The most common method of making absorbent articles breathable is to replace the liquid-impermeable and vapour-impermeable backsheet, which is normally arranged on that side of the article which faces away from the wearer during use, with a microporous liquid-impermeable backsheet which displays vapour-permeability. An example of an absorbent article with a vapour-permeable backsheet is described in, for example, the patent U.S. Pat. No. 4,822,350.
In other absorbent articles, the liquid-impermeable and vapour-impermeable backsheet has been replaced with a backsheet which has conical penetrating capillaries. In these articles, the conical capillaries are oriented so that liquid cannot pass through the capillaries, that is the smallest radius of the conical capillary is oriented towards the wet absorbent absorption core and the largest radius of the capillary is located on that surface of the backsheet which is oriented away from the wet absorbent absorption core. An example of an absorbent article which has a backsheet with conical capillaries is described in patent application WO 00/59436.
Creating an absorbent article with a backsheet which simultaneously has sufficient liquid-impermeability and sufficient breathability is the main problem in the design of the articles described above. In most cases, articles with a microporous backsheet, or with conical penetrating capillaries, have had too poor breathability because the liquid-impermeability of the backsheet was given priority over the breathability. In those cases where the breathability was given priority, major problems have arisen with liquid penetration through the breathable backsheet.
In the patent U.S. Pat. No. 6,090,994, the breathability of the absorbent article has been brought about in a completely different way. The article according to said patent has been provided with an air-exchange, wherein compressible and resilient air pockets are arranged in communication with the air which is present inside the absorption body of the absorbent article. When an article according to said patent is subjected to a pressure, for example when a wearer sits on the article, the air pockets are compressed, the volume of the air pockets being reduced. On compression, the air inside the pockets is forced out into an air-exchange duct system which communicates with the air pockets and opens adjacent to the transverse ends of the article. Arranged at the ends of the article are permeable foam/sponge materials, the air coming out of the air-exchange duct system being able to leave the article through the permeable foam/sponge materials. When the external loading is removed from the absorbent article, the air pockets recover resiliently and new air is sucked into the article via the permeable foam/sponge materials and into the air pockets via the communicating air-exchange duct system.
The compressible and resilient air pockets and the air-exchange duct system have been produced by virtue of a three-dimensional resilient framework being arranged between the absorbent body of the absorbent article and the liquid-impermeable backsheet which is oriented away from the wearer during use. One problem with breathable articles according to U.S. Pat. No. 6,090,994 is that the three-dimensional resilient framework is expensive to produce and difficult to handle in a conventional machine for manufacturing absorbent articles. The design of the three-dimensional resilient framework also means that there is a risk of the absorbent article feeling uncomfortable because the edges of the framework are relatively sharp and can press hard against the thighs of a wearer during use. Another disadvantage is that air exchange inside an absorbent article according to the invention takes place only when the article is subjected to loading essentially at right angles to its plane.
A need still exists therefore for an improved breathable absorbent article which feels comfortable for the wearer and which exchanges air both when the article is subjected to forces in its plane, such as pressure forces from the thighs of the wearer, and when the article is subjected to forces at right angles to its plane, such as forces when the wearer sits on the absorbent article.
There is also a need for a breathable absorbent article which is simple and inexpensive to manufacture and can be manufactured using materials which are conventional for absorbent articles on machines which are conventional for the manufacture of absorbent articles.